In daily life, we only need to know a person's age as long as they know his date of birth; to know how long a civilization has lasted, we only need to find records from the literature.
However, knowing the age of the Earth is a very difficult thing for humans. This is because at the beginning of the birth of the earth, there was no life on the earth, and nature did not leave any traces and records, so that for a long time in the past, there were many opinions about the age of the earth.
Now, through a series of calculations, scientists have found that the earth was born 4.55 billion years ago, and the universe was born 13.8 billion years ago, so the question is: why has no one lived from the birth of the earth to the present, and scientists dare to conclude that the earth has a history of 4.55 billion years.
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In fact, the calculation of the age of the earth has been done for a long time, but they are not based on scientific research, but the Bible, the leader of which is the Archbishop of Ireland Urschel, in 1658, Ursher found through the biblical chronology study that the earth was born on October 22, 4004 BC.
At that time, religion was responsible for explaining the workings of everything in the world, so this statement quickly spread among believers. But this claim was quickly questioned by scientists at the time (scientists at the time did not call themselves scientists, but natural philosophers).
Later, Robert Hooke discovered through fossil research that fossils are not stones that look very similar to certain creatures, but the remains of living creatures, buried in the interior of the earth in geological changes until they are rediscovered, and this process is by no means a simple matter of thousands of years.
Naturalist Bu feng believes that it is likely that the earth was a comet pulling a small piece of melted material from the sun and then forming the earth. But there is a problem that the temperature of the material in the sun is unusually high, and when this material falls to the Earth's surface, it requires a very long cooling time.
By calculating how long it takes for a molten substance as large as Earth to cool to its current temperature, the Earth is at least 75,000 years old. Although this figure does not match the data calculated by scientists today, it is already a pioneer in thinking about problems from a scientific point of view and demonstrating the answers through experiments. To add to this, some people say that Newton once calculated the age of the earth in this way, but because of the large error in this measurement method, it was not adopted.
In addition to Bufeng, Ryle, Hutton, Lord Kelvin, etc. all wanted to measure the age of the Earth, but due to the times, they could not really measure the true age of the Earth until the advent of radiometric dating.
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Back in 1896, Henry. Becquerel discovered radioactive forms. Taking uranium as an example, the nucleus of uranium is larger, it carries more protons, protons are positively charged, due to the rejection of the same kind of charge, it will make the uranium nucleus unstable, until the uranium nucleus disintegrates, releasing high-energy electrons or electromagnetic waves, the number of protons in the uranium nucleus after disintegration will be reduced, the atomic number will become smaller, and therefore, it will decay into lead.
Rutherford found that although we do not know when uranium will crack into lead, but radioactive material has its own decay cycle, we only need to know the radioactive cycle of a substance, and then according to the mixture of the element and its decay, such as: uranium will decay into lead, scientists need to know the proportion of these substances, and then according to the decay cycle of the element can calculate its age. (The actual work is very complicated, involving a lot of specializations).
The half-life of different radioactive substances is different, but scientists can calculate its half-life from the laboratory. Rutherford was keenly aware that radiometric dating could be used as a geological clock, so he measured a sample of uranium in 1904 and concluded that the Earth was 500 million years old.
Today we know that this statement is also incorrect. It was not until the Manhattan Project in the United States that human beings really measured the age of the earth.
We know that the Manhattan Project is to build atomic bombs, the principle of atomic bombs is also nuclear fission, in order to make atomic bombs, scientists must accurately distinguish the isotopes of uranium, so as to produce pure uranium-235 samples.
When scientists can accurately distinguish the isotopes of uranium, they can measure the age of the Earth by radiometric dating. Finally in 1953, Claire. Peterson measured the Age of the Earth at 4.55 billion years from an iron meteorite.
Meteorites are used to measure the age of the Earth because plate movements, volcanic movements, and biological movements often occur on the Earth, so that the rocks on the Earth are constantly reshaped. Meteorites are the material of the early formation of the solar system, it has not been destroyed, so it is the oldest, which can calculate the age of the Earth when it first formed.